Aircrew escape systems

ABSTRACT

A detonating cord is provided, for causing fracture and break-up of an aircraft cockpit canopy for the purpose of emergency escape, consisting of an explosive core contained in a lead casing and surrounded by a plastic sheath, the cord being of substantially semi-circular or D-shaped cross-section. The semicircular surface, but not the flat face, of the casing has several layers of lead tape applied to it within the plastic sheath which lead tape acts as blast-containing and reflecting material to direct the blast effect of the detonation preferentially through the flat-face.

United States Patent [191 Gibb et al.

[ Jan. 1,1974

[ AIRCREW ESCAPE SYSTEMS [75] Inventors: Robert David Gibb, Hessle;Donald Rowand Smith, Kirk Ella; Geoffrey Charles Wickenden, Hull; GrahamNorman Galton, Kingston-upon-Thames; Dennis Robert Shepherd, Bromley,all of England [73] Assignees: Hawker Siddeley Aviation Limited,

' Surrey; Secretary of State for Defence of Great Britain, London, bothof England [22] Filed: Feb. 18, 1972 [21] Appl. N0.: 227,433

[30] Foreign Application Priority Data Feb. 19, 1971 Great Britain5,021/71 [52] US. Cl 102/27 R [51] Int. Cl. C06c 5/04 [58] Field ofSearch 102/24 HC, 27

[56] References Cited UNITED STATES PATENTS 3,241,489 3/1966 Andrew etal 102/24 HC Pike 102/27 R Rush et al. l02/24 HC FOREIGN PATENTS ORAPPLICATIONS 655,92] 8/1951 Great Britain 102/24 HC PrimaryExaminerVerlin R. Pendegrass Attorney-Howard L. Rose et a1.

[ ABSTRACT A detonating cord is provided, for causing fracture andbreak-up of an aircraft cockpit canopy for the purpose of emergencyescape, consisting of an explosive core contained in a lead casing andsurrounded by a plastic sheath, the cord being of substantiallysemicircular or D-shaped cross-section. The semi-circular surface, butnot the flat face, of the casing has several layers of lead tape appliedto it within the plastic sheath which lead tape acts asblast-containingand reflecting material to direct the blast effect of the detonationpreferentially through the flat-face.

7 Claims, 1 Drawing Figure AIRCREW ESCAPE SYSTEMS This invention relatesto the emergency escape of aircrew from an aircraft.

In US. Patent Application Ser. No. 217,896 filed Jan. 14th, 1972 byFrederick John Potts and Geoffrey Charles Wickenden, it is explainedhow, in order to enable an aircrew member to escape through the cockpitcanopy of an aircraft, for instance upon operation of an ejector seat,an explosive cord device, known as 'Miniature Detonating Cord or MDC,may be employed to cause fracture and break-up of the canopytransparency, or at least that area of it through which the aircrewmember will pass. It is also explained that there are difficulties inensuring that such cord exerts its blast energy, upon detonation, in adirection to give good cutting of the canopy material and dispersal ofthe broken fragments out of the path of the escaping crew member,without blow-back of material or undesirable blast pressures beingdirected toward the crew member. And the influence of thecross-sectional shape of the MDC upon this is briefly discussed. It isan object of this invention to provide a novel form of detonating cordwhich is an improvement in these respects.

According to the present invention, the detonating cord is given across-sectional form having at least one flat, and there is embodiedwithin the cord construction at least one layer of blast-containing andreflecting material which extends all around the explosive core of thecord except where the flat lies, so that the blast effect fromdetonation is directed preferentially through the region of the cordperiphery constituted by said flat.

Preferably, the cord is of semi-circular or D-section and theblast-containing and reflecting material is in the form of lead tapeapplied in layers to the curved portion of the outer surface of a leadcasing containing the explosive core. The flat provides a convenientbase surface by means of which the cord can be adhered to the canopytransparency and gives a directional effect to the blast because the airto transparency path is eliminated.

One arrangement in accordance with the invention will now be describedby way of example, with reference to the accompanying drawing, whichshows a miniature detonating cord in cross section.

Referring to the drawing, the explosive filling 42 of the cord iscontained within a formed lead casing 43 semi-circular in cross-section.This can be produce by flattening one side of the circular formresulting from a rolling operation. Attached only to the curvedsemicircular portion of the periphery of the lead casing are a number oflead tapes 44 adhesively secured one upon the other, and the wholeassembly is contained within a heat-shrinkable plastic sheath 45 withadhesive 46 interposed between the sheath and the flat face of the leadcase 43.

It will be understoodthat although this build-up of the cord isdescribed in relation to semi-circular cord a similar technique canequally be applied to rectangular, triangular or other flatted sections,with lead tapes covering the periphery of the inner lead casing exceptfor one flat.

The build-up of the adhesive tape provides a backing such that, althoughthere will still be a tendency to radial blast losses, the presence ofthe lead tape, or any other suitable backing material capable ofproviding the desired blast retention and reflection, will ensure anincreased concentration of the blast effect in the direction of the flatface, which is the face applied contiguously to the canopy surface.

Although such cord can still advantageously be held in place on thecanopy by retaining plates as in the aforesaid US. Patent ApplicationSer. No. 217,896, the development of suitable bonding techniques willpermit the direct attachment of the cord to selected areas of canopysurface, the flat base providing an adequate adhesive area.

This form of MDC may be laid in a pattern on selected areas of canopysurface thus providing for a more predictable fracture. As it is notnecessary to contain this present type of cord within a back-upextrusion such as is described in our aforementioned patent application,the vision loss through a canopy with a pattern-applied MDC will beminimal.

What we claim is: j

l. A detonating cord for producing fracture and break-up of an aircraftcockpit canopy for the purpose of emergency escape, comprising anexplosive core and a completely enclosing sheath surrounding said core,said core and sheath jointly possessing a cross-sectional fonn having atleast one flat, and wherein there is embodied in the cord within thesheath at least one layer of metallic blast-containing and reflectingmaterial which extends all around the explosive core of the cord exceptwhere the flat lies, whereby the blast effect from detonation isdirected preferentially through the region of the cord peripheryconstituted by said flat.

2. A cord according to claim 1, wherein the cord is of substantiallysemi-circular or D-cross-section.

3. A cord according to claim 1, wherein the blastcontaining andreflecting material is, at least in part, in the form of lead tapeapplied in layers.

4. A cord according to claim 3, wherein the layers of lead tape areapplied to a lead casing containing the explosive core.

5. A cord according to claim 1 wherein said sheath is an externalplastic sheath.

6. A cord according to claim 4, wherein adhesive is provided between thesheath and the lead casing in the region of the flat face.

7. A cord according to claim 1, having its flat face held in contiguitywith a canopy surface, e.g. by adhe- SlVe.

1. A detonating cord for producing fracture and break-up of an aircraftcockpit canopy for the purpose of emergency escape, comprising anexplosive core and a completely enclosing sheath surrounding said core,said core and sheath jointly possessing a cross-sectional form having atleast one flat, and wherein there is embodied in the cord within thesheath at least one layer of metallic blast-containing and reflectingmaterial which extends all around the explosive core of the cord exceptwhere the flat lies, whereby the blast effect from detonation isdirected preferentially through the region of the cord peripheryconstituted by said flat.
 2. A cord according to claim 1, wherein thecord is of substantially semi-circular or D-cross-section.
 3. A cordaccording to claim 1, wherein the blast-containing and reflectingmaterial is, at least in part, in the form of lead tape applied inlayers.
 4. A cord according to claim 3, wherein the layers of lead tapeare applied to a lead casing containing the explosive core.
 5. A cordaccording to claim 1 wherein said sheath is an external plastic sheath.6. A cord according to claim 4, wherein adhesive is provided between thesheath and the lead casing in the region of the flat face.
 7. A cordaccording to claim 1, having its flat face held in contiguity with acanopy surface, e.g. by adhesive.